JPH07104295B2 - Method for measuring crystal defect density and precipitated oxygen concentration of single crystal substrate for semiconductor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a crystal of a semiconductor single crystal substrate for measuring a crystal defect density by an X-ray diffraction intensity of the single crystal substrate automatically obtained by an X-ray diffraction analysis method. The present invention relates to a defect density measuring method and an oxygen precipitation amount measuring method for a semiconductor single crystal substrate for measuring an oxygen precipitation amount.

2. Description of the Related Art Conventionally, as a method for measuring the crystal defect density of a single crystal substrate for semiconductor, generally, observation by an optical microscope has been performed.

In this method using an optical microscope, the microscopic surface of the single crystal substrate is immersed in an etching solution (mixed acid of HF and HNO ₃ ) for about 10 minutes to perform etching, and then washed with water for 10 minutes. Then, it is immersed in an etching solution (mixed acid of HF, HNO ₃ , CH ₃ COOH, and AgNO ₃ ) for about 10 minutes to perform selective etching, and then rinsed with water for 10 minutes.

After performing the above etching treatment, the microscopic surface of the sample is observed with an optical microscope, and the crystal defects are counted to determine the crystal defect density of 1c.
It was represented by the number of defects per m ² .

Further, as a method for measuring the amount of oxygen precipitation of a single crystal substrate for a semiconductor, conventionally, an initial oxygen concentration of the single crystal substrate for a semiconductor is measured by an infrared absorption method, and a heat treatment is applied to the same sample to precipitate oxygen and the residual Measure oxygen concentration. Then, the amount of precipitated oxygen was obtained from the difference between the initial oxygen concentration and the residual oxygen concentration.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, the crystal defect density of a single crystal substrate is conventionally observed by an optical microscope, but this method requires about 1 hour for pretreatment such as etching of a sample, It also takes time. Moreover, there were individual differences in the speculum, and there was an error in the number of counts.

Further, the conventional method for measuring the amount of oxygen precipitation of a single crystal substrate is an effective method for a single crystal substrate having a normal resistance of 1 Ωm or more. However, since a minority carrier has an effect on a low-resistance single crystal substrate having a resistance value of 1 Ωm or less, it is very difficult to measure the oxygen concentration, and the oxygen precipitation amount cannot be easily measured.

In view of the present situation, the present invention uses the X-ray diffraction analysis method, does not require a long-term pretreatment, and is based on the X-ray diffraction intensity detected easily and automatically, and the crystal of the single crystal substrate is obtained. It proposes a method for measuring the defect density and a method for measuring the amount of oxygen precipitation of a low resistance single crystal substrate.

Means for Solving the Problems In order to achieve the above object, the crystal defect density measuring method of the present invention counts the X-ray diffraction intensity of a single crystal substrate set in advance for each required size by an X-ray diffraction analysis method. With
The single crystal substrate was mirror-etched, crystal defects at the same location as the X-ray diffraction were counted by an optical microscope, the relationship between the X-ray diffraction intensity and the crystal defect count was obtained, and the single crystal substrate to be measured was obtained. The crystal defect density is obtained by converting the X-ray diffraction intensity into a crystal defect count based on the relationship obtained in advance according to the size.

The method for measuring the concentration of precipitated oxygen according to the present invention counts the X-ray diffraction intensity of a single-crystal substrate of normal resistance set in advance for each required size by X-ray diffraction analysis and absorbs the single-crystal substrate with infrared rays. The oxygen concentration at the same place as the X-ray diffraction is measured by the method, the relationship between the X-ray diffraction intensity and the concentration of precipitated oxygen is obtained in advance, and the X-ray diffraction intensity obtained for the single crystal substrate to be measured is compared with the above-mentioned size. From the relationship obtained in advance according to
It is characterized in that the concentration of precipitated oxygen of the normal resistance and low resistance single crystal substrates for semiconductors is measured in terms of the concentration of precipitated oxygen.

The X-ray diffraction intensity in the present invention is automatically detected by using an X-ray topography (Lang method) device. That is, using this device, the conditions are automatically adjusted to the place where the diffraction intensity is the strongest at each place of the sample, and a composite image by the diffracted X-ray is projected. The intensity line is read out laterally at the required location in this composite image, and the diffraction intensity at the specific location can be known from this.

Moreover, the X-ray intensity was measured by preparing one standard single crystal substrate,
After setting the slit width so as not to cut the line, the X-ray intensity is measured, and the intensity is measured as the X-ray standard intensity at each measurement.

That is, the standard single crystal substrate generates X-rays so that the diffraction intensity is always the same as the previous measurement by using this standard sample in order to keep the X-ray intensity used for measurement constant. It is for adjusting kV and mA of the device.

In the present invention, the relationship between the X-ray diffraction intensity of a single crystal substrate and the crystal defect count number, which is obtained in advance, is that the X-ray diffraction intensity has different absorption ratios with respect to X-rays depending on the thickness of the substrate to be measured. Since the thickness is unified by each size of 4 inches, 6 inches, and 8 inches, it is necessary to obtain the above relationship for each size.

In the case of the crystal defect density measuring method, the relationship between the X-ray diffraction intensity and the crystal defect count number is as follows: X-rays are projected on the standard single crystal substrate set for each size by the above method to count the X-ray diffraction intensity. Further, after etching the same portion of the substrate related to X-ray diffraction, crystal defects are measured by microscopic examination with an optical microscope, and the relationship between the X-ray diffraction intensity and the crystal defect count number is obtained from this. When this relationship is graphed as in the example, X obtained separately for the single crystal substrate to be measured is obtained.
The line diffraction intensity can be converted to the crystal defect count from the above graph to obtain the crystal defect density, and, in the case of data processing by a computer as shown in the example,
The relational expressions and the like of the above graphs are set so that they can be compared and converted by a known processing method that is equivalent to graphing and comparing and converting.

Further, in the case of the method for measuring the concentration of precipitated oxygen, X-rays are projected onto the standard single crystal substrate set for each size by the above method to count the X-ray diffraction intensity, and the same portion of the substrate involved in the X-ray diffraction is measured. The initial oxygen concentration and the residual oxygen concentration are measured by the infrared absorption method, and the oxygen concentration is measured from the difference, and the relationship between the X-ray diffraction intensity and the crystal defect count number is obtained from this difference. When graphed as in the example, the X-ray diffraction intensity obtained separately for the single crystal substrate to be measured is
The crystal defect density can be obtained by converting the crystal defect count from the above graph.

Effect The present invention measures the crystal defect density and the concentration of precipitated oxygen based on the X-ray diffraction intensity of the single crystal substrate obtained by the X-ray diffraction analysis method. Therefore, it is simple to perform X-ray projection on the sample to be measured. It can be measured in a short time by operation.

Examples Example 1 An example of a crystal defect density measuring method for a semiconductor single crystal substrate will be described with reference to the drawings.

As shown in FIG. 1, X generated from the X-ray generation source (1)
A line is projected onto the inspection object (4) through each slit of the slit plates (2) and (3), and the diffracted X-ray is projected onto the fluorescent plate (6) through the slit of the slit plate (5). The object to be inspected (4) and the fluorescent plate (6) are synchronously scanned to form a diffraction image on the fluorescent plate (6). Further, a counter (7) is installed on the back side of the fluorescent plate (6), and the diffraction intensity at each place is measured as the brightness of the fluorescent plate with reference to the place where the diffraction intensity obtained by a standard sample is the strongest.

Now, with respect to a single crystal substrate having a diameter of 4 inches (10, 16 cm) and a thickness of 625 μm, X-rays were continuously projected on the diameter line to obtain the X-ray diffraction intensity. On the other hand, the same place corresponding to the diffraction intensity test of the single crystal substrate was etched and then microscopically observed with an optical microscope to count crystal defects.

Then, the relationship between the X-ray diffraction intensity and the crystal defect count was graphed. The graph is shown in FIG.

X-ray projection was performed on the diameter line of the single crystal substrate for which the crystal defect is to be measured by using the X-ray topography shown in FIG. 1, and the intensity of the diffracted X-ray at each position was obtained. The results are shown in Table 2.

In FIG. 2, the horizontal axis represents the intensity on the diameter line of the single crystal substrate, and the vertical axis represents the intensity with the strongest position of the diffracted X-ray as a reference (indicated by numerical value 1).

The X-ray diffraction intensity corresponding to each position on the horizontal axis in FIG. 2 can be taken out as a data value from a computer. For example, the diffraction intensity at the position 110 in FIG. 2 is 5 × 10 ^{3 when} read from the data value, and the defect density can be derived as 11 × 10 ⁵ from FIG.

Example 2 An example of a method for measuring the concentration of precipitated oxygen in a semiconductor single crystal substrate will be described with reference to the drawings.

Now, the X-ray diffraction intensity was obtained by projecting X-rays on a single crystal substrate having a diameter of 5 inches (12.7 cm) and a thickness of 625 μm using the X-ray topography apparatus shown in FIG. On the other hand, the initial oxygen concentration and the residual oxygen concentration at the same location corresponding to the diffraction intensity measurement location of the single crystal substrate were measured by the infrared absorption method, and the oxygen precipitation amount was obtained from the difference. Then, the relationship between the X-ray diffraction intensity and the oxygen precipitation amount was graphed. The graph is shown in FIG.

Then, on the single crystal low resistance substrate for which the amount of precipitated oxygen should be measured,
X-ray projection was performed using the X-ray topography apparatus shown in FIG. 1, and the intensity of the diffracted X-ray at each position was obtained. The results are shown in FIG. 2 as in Example 1.

In FIG. 2, for example, when the intensity at the position A is calculated, it is 0.8. This maximum intensity is 6300, which is 5000 when converted to the X-ray diffraction intensity in FIG. From this, the amount of precipitated oxygen is about 8 × 10 ¹⁷ atoms / cc. That is, the oxygen precipitation amount of the low resistance substrate at the above position is 8 × 10 ¹⁷ atoms / cc.

EFFECTS OF THE INVENTION The inventions of claims 1 and 2 both count the X-ray diffraction intensity of a single crystal substrate by an X-ray diffraction analysis method, and in claim 1, a graph showing the relationship between the X-ray diffraction intensity and the crystal defect count number. The X-ray diffraction intensity of the sample to be measured is converted by Further, in claim 2, the X-ray diffraction intensity obtained for the sample to be measured is converted by a graph showing the relationship between the X-ray diffraction intensity and the concentration of precipitated oxygen. Therefore, in both claims 1 and 2, it is possible to measure the crystal defect density or the concentration of precipitated oxygen in a short time by a simple operation of only projecting X-rays on the sample to be measured. Further, according to the invention of claim 2, it is possible to easily obtain the oxygen precipitation amount of the single crystal substrate for low resistance semiconductor which is difficult to measure by the infrared absorption method.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the principle of an X-ray topography apparatus used for X-ray diffraction in the present invention, and FIG. 2 is obtained by continuous X-ray projection on a diameter line of a single crystal substrate to be measured whose crystal defect density is to be obtained. FIG. 3 is a graph showing the relationship between the X-ray diffraction intensity of the standard single crystal substrate in the invention of claim 1 and the crystal defect count number, and FIG. 4 is a graph of the normal resistance in the invention of claim 2. 6 is a graph showing the relationship between the X-ray diffraction intensity of a single crystal substrate and the concentration of precipitated oxygen. 1 ... X-ray source, 2, 3, 5 ... Slit plate 4 ... Inspected object, 6 ... Fluorescent plate 7 ... Counter

Claims (2)

[Claims] 1. An X-ray diffraction analysis method is used to count the X-ray diffraction intensities of a single crystal substrate set in advance for each required size, and the single crystal substrate is mirror-etched to obtain the X-ray diffraction by an optical microscope. The crystal defects in the same place are counted, the relation between the X-ray diffraction intensity and the crystal defect count is obtained, and the X-ray diffraction intensity obtained for the single crystal substrate to be measured is calculated from the relation obtained in advance according to the size. , A method for measuring the crystal defect density of a single crystal substrate for a semiconductor, which is obtained by converting the crystal defect count into the crystal defect density. 2. An X-ray diffraction analysis method is used to count the X-ray diffraction intensity of a single-crystal substrate of ordinary resistance set in advance for each required size, and the single-crystal substrate is subjected to the X-ray diffraction analysis by an infrared absorption method. The oxygen concentration in the same place is measured, the relationship between the X-ray diffraction intensity and the precipitated oxygen concentration is obtained, and the X-ray diffraction intensity obtained for the single crystal substrate to be measured is obtained in advance according to the size. A method for measuring the concentration of deposited oxygen in a single crystal substrate for a semiconductor, which converts the concentration of deposited oxygen in the single crystal substrate for a semiconductor having a normal resistance and a low resistance.